The present invention relates to a method of configuring transmission data streams and a wireless communication system, and more particularly, to a method and a wireless communication system capable of determining a number of transmission data stream in a noncontiguous operation mode.
As a demand for wireless service increases, a data rate of a wireless device is required to be higher. The wireless device may include multiple antennas to provide multiple spatial data streams, so as to enhance the data rate. In addition, an operating bandwidth of the wireless device is expected to be wider as well. In reality, since the frequency spectrum is densely occupied, especially the Industrial Scientific Medical (ISM) spectrum, it is hard to obtain a contiguous and sufficiently wide bandwidth to enhance the data rate. Recently released wireless standard allows wireless devices to operate over two or more noncontiguous frequency bands. For example, a wireless device under IEEE 802.11ac is allowed to perform wireless transmission over two noncontiguous 80 MHz bands simultaneously, which is equivalent to a 160 MHz band, so as to widen an equivalent operation bandwidth and improve the data rate.
Nevertheless, performing wireless transmission over a plurality of noncontiguous frequency bands requires more radio frequency (RF) units, where each RF unit may include an antenna and a transmission/reception switch to selectively connect the antenna either to a transmission processing circuit or to a reception processing circuit, since the noncontiguous frequency bands have different central frequencies. Note that, multiple RF units/antennas included in the wireless device are originally intended for providing multiple spatial data streams in a first frequency band of the plurality of noncontiguous frequency bands. Utilizing the RF units to operate at different central frequencies would decrease a number of data streams in the first band.
For example, a first wireless device equipped with two RF units is capable of providing two spatial data streams in the first frequency band. When the first wireless device is configured to operate over the first frequency band and a second frequency band simultaneously, where the first frequency band and the second frequency band are noncontiguous, one RF unit is designated for one frequency band. Hence, in the first frequency band, the first wireless device is limited to provide only one data stream.
Under such a condition, when a second wireless device establishes a wireless connection with the first wireless device on the first frequency band, the first wireless device is clamped to provide only one data stream to the second wireless device in the first frequency band, even though the second wireless device is equipped with two or more RF units. That is, even though both the first and the second wireless device have spatial capability of providing multiple data streams transmission, there is still only one data stream transmitted between the first and the second wireless device in the first frequency band. Part of the RF units of the wireless devices are left unused, and the data rate enhancement brought by multiple input multiple output (MIMO) is limited.
Therefore, it is necessary to improve the prior art.